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Topic Review (Newest First)

02-23-2013 07:37 PM

vinniekq2

The rear axle ratio needs to match the purpose of the car. I use a 3.50 gear with 27 1/2 tall tires with a standard. floor it in first or second and the tires break loose.

02-23-2013 07:33 PM

vinniekq2

Have you ever seen a race car with mufflers go faster than a similar car with open headers? 3 inch!
also if your engine revs 6500 rpm,your headers are also too small

Then I can answer that. As much "detail" as you're willing to share. What style rear axle?

X 2 on the "X" pipe. A lot of our Pontiac guys use Pypes. I've heard good and bad. The X-pipe definitely makes power, though.

Jim

02-23-2013 03:59 PM

gearheadslife

2.5" mandrel bent pipe with x pipe..
from the x junction you have 5" for thet pulse to feed to.. more than anough for a 406

02-23-2013 03:43 PM

macrobert68

Quote:

Originally Posted by macrobert68

dart shp 72 cc

what kind of gear would u use .i was thinking 373 0r 410

02-23-2013 03:38 PM

macrobert68

dart shp 72 cc

02-23-2013 03:21 PM

Mr. P-Body

Yes, there will be a loss of low-end torque with a larger system (this engine doesn't appear to make much low-end, though). We tend to recommend, for maximum performance, and not necessarily the "sound", stay with 2 1/2" pipe until CID gets up around 500.

Particularly with smaller headers like you have, you need that "step" in the pipe to increase exit velocity. For "driving" (street use), this is important. If it's a dedicated race car that requires an exhaust system, then yes, 3".

BTW, those headers are awefully small for a 7,000 RPM 400. Just my opinion. I'd like to see 1 7/8" units on there. Upper end power would significantly increase. Regardless, this car will need some "stiff" gear to be a decent driver. What heads are they?

Jim

02-23-2013 10:49 AM

OneMoreTime

For your setup I would go with the 3 inch..I don't think you would lose that much on low end and your engine setup is for midrange and top end power..

Sam

02-23-2013 09:58 AM

macrobert68

Quote:

Originally Posted by DanielC

You are going to get a lot of theory, and ideas on this, and some of the advise may actually be true.
But with so much misinfornation existing, and being reproduced by people on the web, the only way to know is to spend lots on time on a chassis dyno, with different exhaust configurations.

yea i can understand that .
but i cant remember if the larger the exhaust is for top end speed or low end tork.

02-23-2013 09:54 AM

DanielC

You are going to get a lot of theory, and ideas on this, and some of the advise may actually be true.
But with so much misinfornation existing, and being reproduced by people on the web, the only way to know is to spend lots on time on a chassis dyno, with different exhaust configurations.